A series of films deposited under different O partial pressures and annealed under

different atmospheres were prepared to investigate the role of O vacancies in tuning magnetic properties of Co-doped SnO2 films. The inclusive Co in SnO2 was in the 2+ state and substitutes for the Sn4+ site. Intrinsic room temperature ferromagnetism was observed in all films, which was not carrier mediated, but coexists with the dielectric behavior. A maximum magnetic moment of 2.37µB/Co was achieved by vacuum annealing due to the increase and diffusion of O vacancies rather than the improvement of crystallinity of the film, and the magnetic moment decreased considerably after air annealing or increasing the O partial pressure during deposition. The changes of O vacancy concentration and distribution were indirectly demonstrated by the relative shifts of Co 2p3/2 peaks in X-ray photo-electron spectra. The band gap of Co-doped SnO2 film was larger than that of pure SnO2 film, suggesting the influence of inclusive Co on the electronic states, and further blue-shift after annealing was also visible. The F-center model was modified to explain the ferromagnetism in insulating Co-doped SnO2 films.

Role of Oxygen Vacancies in Tuning Magnetic Properties of Co-Doped SnO2 Insulating Films. X.F.Liu, Y.Sun, R.H.Yu: Journal of Applied Physics, 2007, 101[12], 123907